Cutting Off Sediment at the Source

An example of soil erosion. Effective erosion control at construction sites helps maintain water quality while reducing erosion-related cost overruns and project delays.

EPA's new effluent limitations guidelines require larger construction sites to limit sediment in stormwater discharges to 280 nephelometric turbidity units (NTU). This image shows what stormwater samples look like at different NTU levels — from pollutant-free water to nearly opaque, polluted water. From left: 0 NTU, 20 NTU, 100 NTU, and 800 NTU. Photos: Brian Wanzenried

Sedimentation basins are used to capture coarse sediment from storm flows, and temporarily detain stormwater so that the velocity of storm flows is reduced and the sediment falls. Maintenance is required to clean out sedimentation basins, like the one shown below, after storms — otherwise they fill up with sediment, causing the walls to erode.

This table shows the EPA's hierarchy of pollution-prevention techniques from most to least preferred. The Pollution Prevention Act of 1990 also lists source reduction as a preferred method of pollution control over recycling, treatment, and disposal.

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